A process and reactor for producing chlorine dioxide are known from European Pat. No. 0 095 199 and Published German Application No. 37 19 878. Reference may also be had to U.S. patent application Ser. No. 06/942,522 filed Dec. 16, 1986 now abandoned and the Continuation U.S. application thereof, Ser. No. 07/170,665 filed Mar. 10, 1988, now U.S. Pat. No. 4,851,198.
The reaction is preferably effected in accordance with the reaction equation 2NaClO.sub.3 +4HCl=2ClO.sub.2 +Cl.sub.2 +2NaCl+2H.sub.2 O.
HCl serves advantageously as an acid and as a reducing agent so that there is no need for a separate addition of reducing agent if hydrochloric acid is used.